If the Bounty Manager knew that the project is scam and still promoted it than they deserve a negative trust.
But if they didn't knew about that, they are no different from bounty participants as they get paid to advertise.
If bounty manager are to be given negative trust for working on a scam project, bounty participants too deserve one as they too promote for payment.
I agree with you, mostly bounty manager is the employee who earns the salary so as soon he/she gets his money he writes answers in TG, here but when scam ICO's show the real face and stop paying him he abandons the project (by the way it's the sign of scam bounty).
So BM usually have the same information as bounty hunters, if he is in the team i vote for to make list of scammers.